The phagocytosis associated metabolic, enzymatic and antimicrobial processes of leukocytes collected from animals x-irradiated at selected hematopoietic organs will be investigated. Attempts will be made to localize biochemical lesions associated with antimicrobial activity in the phagocytes of these subjects. For this, the mature leukocytes (PMN, macrophage and lymphocytes), their precursors (bone marrow, spleen and thymus cells) and cellular fractions will be studied. The information gathered from the animal investigations will be applied to the study of cells collected from patients undergoing radiotherapy. Special emphasis will be given to studies of the intra- and extracellular distribution of peroxidase and its relation to antimicrobial activity. A systematic and indepth study of the critical processes involved in glucose and H2O2 metabolism at rest and during phagocytosis and of peroxidase-H2O2-antimicrobial systems will be carried out. Investigation initially on animals and later on patients, before, during, and after x-irradiation, is planned. This approach, hopefully, will result in information applicable to the infection prone subjects with neoplastic and other disorders.